在我们想要使用一个实体类的时候，如果发现创建这个类的时候，给某一些字段设置了初始值（某些场景下的特殊需要），但我们这个时候又不需要这些初始化值的时候，我们就会想要把这些值全部清除掉，让其变为一个干净的类，我们可以手动一个一个去赋null值，我一开始就是这么做的，同事看到后告诉我，你可以尝试使用反射机制，自己封装一个工具类，这样大家都可以使用，于是我就这么做了，也就有了下面比较low B 的代码：
我的代码：
public static void reflectClassValueToNull(Object model) throws Exception {
//获取此类的所有父类
List<Class<?>> listSuperClass = Lists.newArrayList();
Class<?> superclass = model.getClass().getSuperclass();
while (superclass != null) {
if (superclass.getName().equals("java.lang.Object")) {
break;
}
listSuperClass.add(superclass);
superclass = superclass.getSuperclass();
}
//遍历处理所有父类的字段
for (Class<?> clazz : listSuperClass) {
Field[] fields = clazz.getDeclaredFields();
for (int i = 0; i < fields.length; i++) {
String name = fields[i].getName();
Class type = fields[i].getType();
Method method = clazz.getMethod("set" + name.replaceFirst(name.substring(0, 1),
name.substring(0, 1).toUpperCase()), type);
method.invoke(model, new Object[]{null});
}
}
//处理此类自己的字段
Field[] fields = model.getClass().getDeclaredFields();
for (int i = 0; i < fields.length; i++) {
String name = fields[i].getName();
Class type = fields[i].getType();
//获取属性的set方法
Method method = model.getClass().getMethod("set" + name.replaceFirst(name.substring(0, 1),
name.substring(0, 1).toUpperCase()), type);
//将值设为null
method.invoke(model, new Object[]{null});
}
}代码写完的那一刻，真的很爽，虽然这个东西比较简单，但还是有一点成就感。然后告诉同事我写好了，让他帮忙优化一下（毕竟他在我心里是一个真正的大牛），午休结束后，他发来了两个方法给我，以不同的方式实现，不过都是基于反射机制。以下是他的代码：
public static <T> T byMethod(T t) {
ReflectionUtils.getAllMethods(t.getClass(), method -> Objects.requireNonNull(method).getName().indexOf("set") == 0).forEach(method -> {
try {
method.invoke(t, new Object[]{null});
} catch (IllegalAccessException | InvocationTargetException e) {
throw new RuntimeException(e);
}
});
return t;
}public static <T> T byField(T t) {
ReflectionUtils.getAllFields(t.getClass()).forEach(field -> {
try {
field.setAccessible(true);
field.set(t, null);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
}
});
return t;
}所以，差距你们看到了吗？反正我看到了！
package com.chryl.util;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
public class ReflectionUtils {
/**
* 将实体类中的String类型属性为null的置为""
*
* @param o
* @return
*/
public static Object nullifyStrings(Object o) {
Field[] declaredFields = o.getClass().getDeclaredFields();
for (Field f : declaredFields) {
f.setAccessible(true);
String name = f.getName();
if ("serialVersionUID".equals(name)) {
continue;
}
//获取属性类型
Class type = f.getType();
try {
//只操作String类型
if (type.equals(String.class)) {
String value = (String) f.get(o);
//如果为空
if (value == null || value.trim().isEmpty()) {
//获取属性的set方法
Method method = o.getClass().getMethod("set" + name.replaceFirst(name.substring(0, 1), name.substring(0, 1).toUpperCase()), type);
// f.set(o, null);
//将值设为空串
method.invoke(o, "");
}
}
} catch (Exception e) {
throw new RuntimeException(e);
}
}
return o;
}
/**
* 含递归
* 将实体类中的 String类型或对象 属性为null的置为""或空对象
*
* @param o
* @return
*/
public static Object nullifyObjectOrStrings(Object o) throws ClassNotFoundException {
Field[] declaredFields = o.getClass().getDeclaredFields();
for (Field f : declaredFields) {
f.setAccessible(true);
String name = f.getName();
if ("serialVersionUID".equals(name)) {
continue;
}
//获取属性类型
Class type = f.getType();
try {
//获取属性的set方法
String setterMethod = "set" + name.replaceFirst(name.substring(0, 1), name.substring(0, 1).toUpperCase());
Method method = o.getClass().getMethod(setterMethod, type);
//只操作String类型
if (type.equals(String.class)) {
String value = (String) f.get(o);
//如果为空
if (value == null || value.trim().isEmpty()) {
// f.set(o, null);
//将值设为空串
method.invoke(o, "");
}
} else {
Class<?> aClass = Class.forName(f.getGenericType().getTypeName());
Object createObj = aClass.newInstance();
//实体赋值
method.invoke(o, createObj);
nullifyObjectOrStrings(createObj);
}
} catch (Exception e) {
throw new RuntimeException(e);
}
}
return o;
}
}package com.chryl.test;
import com.chryl.entity.User;
import com.chryl.util.ReflectionUtils;
/**
* Created By Chryl on 2021-08-11.
*/
public class NullStrTest {
public static void main(String[] args) throws Exception {
User user = new User();
User user1 = (User) ReflectionUtils.nullifyStrings(user);
System.out.println(user1);
User user12 = (User) ReflectionUtils.nullifyObjectOrStrings(user);
System.out.println(user12);
}
}package com.chryl.entity;
import java.io.Serializable;
/**
* Created By Chryl on 2021-08-11.
*/
public class User implements Serializable {
private static final long serialVersionUID = 930878416859194735L;
private String username;
private String password;
private String age;
private ParamsList paramsList;
public User() {
}
public User(String username, String password, String age) {
this.username = username;
this.password = password;
this.age = age;
}
public User(String username, String password, String age, ParamsList paramsList) {
this.username = username;
this.password = password;
this.age = age;
this.paramsList = paramsList;
}
public static long getSerialVersionUID() {
return serialVersionUID;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
public ParamsList getParamsList() {
return paramsList;
}
public void setParamsList(ParamsList paramsList) {
this.paramsList = paramsList;
}
}package com.chryl.entity;
/**
* Created By Chryl on 2021-08-12.
*/
public class ParamsList {
private String param1;
private String param2;
private String param3;
private String param4;
public ParamsList() {
}
public ParamsList(String param1, String param2, String param3, String param4) {
this.param1 = param1;
this.param2 = param2;
this.param3 = param3;
this.param4 = param4;
}
public String getParam1() {
return param1;
}
public void setParam1(String param1) {
this.param1 = param1;
}
public String getParam2() {
return param2;
}
public void setParam2(String param2) {
this.param2 = param2;
}
public String getParam3() {
return param3;
}
public void setParam3(String param3) {
this.param3 = param3;
}
public String getParam4() {
return param4;
}
public void setParam4(String param4) {
this.param4 = param4;
}
}以上为个人经验，希望能给大家一个参考，也希望大家多多支持。
